Virtual Special Issue Preface: Forest Response to Environmental Stress: Impacts and Adaptation.

The current distribution of forest typeswas largely established at the beginning of the Holocene epoch (approximately 12,000 BCE), but forests are constantly in flux. Many regional scale stresses (e.g., drought, heat, fire, and insect) and even a few multi-regional or global stresses (e.g., 8200 BCE cooling, or themedieval warming period) have occurred over the past 12 millennia. However, modern ecology is less than 200 years old, and large-scale anthropogenic impacts on climate are mainly confined to the latter half of the 20th century. Given the large number of potential climate, geographic, demographic combinations, and relatively short time of study, we should not be surprised that there are an increasing number of observed environmental stresses with no antecedent point of reference. Chronic anthropogenic stressors (e.g., elevated nitrogen, sulfur and heavy metal deposition, and tropospheric ozone) have mentality precondition human thought to accept these impacts as part of the environmental condition in the areas in which they occur. Therefore, the acceptance of non-antecedent variability is part of the challenge associated with climate change in which variability exceeds historic observation. This desensitizing of human reaction to disturbance impedes societies' ability to acknowledge unprecedented environmental change, and thereby delaysmeasures to reduce or adapt to these non-antecedent stresses. A poor understanding of non-antecedent stress also contributes to the challenges of addressing these unprecedented disturbances. Non-antecedent forest stressors can be divided into the three categories of 1) new individual stressors; 2) record stressors; or 3) integrated stressors. New stressors are those that have not been previously observed within an ecosystem or region. To better understand their potential negative impacts, researchers can exchange space for time. Examples include 21st Century ozone, and, heavy metal and acidic deposition in East Asia. In these instances, heavy metal disturbance impacts from Eastern Europe and ozone impacts from the United States southwest Pacific region during the 1960s–1980s provide some guidance. This STOTEN special issue contains several papers of local to regional scale new stress impacts that can provide guidance for both the study locations and potentially forest areas under similar, current or future stresses. Record stressors pose a second challenge to understanding and developing ecosystem resilience adaptation measures. However, as with techniques to better understand new impacts, understanding locally non-antecedent record forest stress can again substitute space for time. For example, recent surface air warming is unprecedented in the Russian taiga, but similar record heat has occurred in both Canadian and United States taiga forests. Therefore, like non-antecedent new disturbances, non-antecedent record disturbance impacts can also ex-